1. Field of the Invention
The present invention relates generally to switches and use of switches for controlling an apparatus and/or a multiplexer. More particularly, the present invention relates to a switch whose output status changes in response to a predetermined rate-of-change of an output signal, and to controlling both switching and proportional functions of an apparatus and/or a multiplexer in response to output signals.
2. Description of the Related Art
In recent years there has been an increasing awareness of the importance, not only providing for the needs of handicapped persons, but also of utilizing them as productive members of society, rather than keeping them partially or wholly dependent upon others.
Fortunately, this enlightened view has coincided with giant strides in technology, particularly electronics and computed-based technology, and this increase in technology has been reflected by giant strides in electrically-propel led wheelchairs.
The prior art includes electrically-propelled wheelchairs in which control of start, stop, and steering has been achieved by manually-actuated X-Y transducers, commonly called “joysticks.”
Lautzenhiser et al., in U.S. Pat. No. 4,906,906, issued 6 Mar. 1990, and in U.S. Pat. No. 4,978,899, issued 18 Dec. 1990, teach wheelchairs that are propelled by pulse-width-modulated voltages, that are dynamically braked by shorting the motors, that are made freewheeling without the expense and complexity of a clutch, and in which tremor control is provided, so that those who have hand tremors can easily and accurately control power wheelchairs.
The prior art includes attempts to control wheelchairs by sipping or puffing on a tube. However, controllability of sip-and-puff units has been marginal, especially for those who depend upon a respirator or ventilator for breathing, since they can puff into a tube only while exhaling, and sipping is even more difficult.
In U.S. Pat. No. 5,635,807, which issued on 3 Jun. 1997, Lautzenhiser teaches electric control systems that provide nonlinear relationships between X-Y mechanical inputs and resultant differential speeds of two propulsion motors. These nonlinear relationships between X-Y mechanical inputs and electrical outputs allow many handicapped persons, who otherwise would be limited to sip-and-puff systems, to control a wheelchair by joystick movement.
Perhaps even more significantly, when a joystick is replaced with two tiny transducers or input devices that are mounted to a person's head, or to an other body member, these nonlinear relationships allow easy and accurate control of both speed and steering of power wheelchairs by means of body-component movements. For instance, a person who is paralyzed from the neck down can perform all control functions of an electrically propelled wheelchair except for connecting and disconnecting power to the system.
In U.S. Pat. No. 5,635,807, Lautzenhiser also provides adjustable transducer sensitivity, steering sensitivity control that is adjustable, selectively-adjustable signal limiting so that maximum speeds can be selectively adjusted, and overrange shutdown.
In U.S. patent application Ser. No. 09/652,395, filed 31 Aug. 2000, Lautzenhiser et al. teach a tilt-axis X-Y input device that may be mounted to a body component, such as the head or a hand of a user, null compensators that automatically compensate for errors in attaching the X-Y input device to a head or other body component, a null-width generator that adjustably provides a neutral zone to help an operator find and hold a neutral position, a turn-signal conditioner that provides easier control of turns including elimination of “fishtailing,” tremor control for those with body tremors, adjustable tilt-axis sensitivity to selectively match the motor skills of the user, and overrange shutdown as a safety feature.
In the same patent application, Lautzenhiser et al. teach control of a second device, such as a computer and its cursor, both of which may utilize voice-recognition technology to provide the required switching functions.
Even with the great strides that have been provided by head and other body-component control of both speed and turns of power wheelchairs, much still needs to be accomplished. Many still are unable to control their own safety except by the use of a call button. Many are unable to control their own comfort and productivity needs, such as adjusting leg supports, head supports, backrests, heating, cooling, and lighting. And many are unable to control productivity devices, such as computers, and entertainment devices, such as radio or television.
It is these other safety, comfort, productivity, and entertainment needs that the present patent application addresses.
In the industry, apparatus for controlling safety, productivity, comfort, and entertainment devices have been called “Environmental Control Units” (ECU). Therefore, this terminology is used extensively in the detailed description.